From the Magazine

The Mother Lode

The tropics are renowned bastions of biodiversity. But scientists are finding that our own backyard rivals the rainforests as they uncover dozens of new species each year in Great Smoky Mountains National Park.

The bright-red immature fruiting bodies of this slime mold, Tubifera ferruginosa, stand out against the dark, decaying log. In temperate forest such as those in the Smokies, most slime mold fruitings live on rotting wood. These fruiting bodies are unusually large, with the biggest about an inch across. Photo: Coke Whitworth

If scientists can fairly and properly be compared to prospectors—and in light of the bioprospectors who mine the world for beneficial and commercially viable extremophiles, that analogy seems apt—then they’ve struck the mother lode in a misty range of mountains in a most unlikely locale. In slightly more than a decade of fieldwork they’ve discovered more than 900 species previously unknown to science in a landscape that has long been staring them right in the face. Oval in shape, roughly 800 square miles covering the Tennessee-North Carolina border like a rumpled blanket, and traipsed upon by some nine million people each year, Great Smoky Mountains National Park has proved to be an unassuming wellspring of biological diversity.

Often veiled in vapory tendrils, the park has demonstrated that we don’t know quite as much about our resident life-forms as we might think. Since Great Smoky launched its All Taxa Biological Inventory (ATBI) in 1998, at least 907 species new to science and more than 6,500 species previously undetected in the park have been snared, netted, scooped, trapped, and observed by an array of more than 1,000 biologists, entomologists, taxonomists, botanists, and other “ologists.” Armed with bug nets, funnel traps, light traps, and climbing gear to both ascend into forest canopies and descend into caves, degreed scientists and volunteer “citizen scientists” have catalogued thousands of species, big and small, known and previously unknown, and all with ecological roles in the park. Among the newcomers are 27 species of freshwater crustaceans and crayfish, a large variety of arachnids of both the terrestrial and aquatic variety, 74 species of flitting moths and butterflies, 42 species of beetles, 23 varieties of bees, and 78 algae species. The successes realized in Great Smoky have spurred other ATBI efforts at Acadia National Park, Big Thicket National Preserve, Boston Harbors National Recreation Area, Canyon de Chelly National Monument, Congaree National Park, Yellowstone National Park, and the Santa Monica Mountains National Recreation Area.

Though the numbers are important, the inventory is more than an exercise in counting. It’s intended to gain a better understanding of the Great Smokies ecosystem and, along the way, raise people’s curiosity—and perhaps even their knowledge—about the world around us. Working to pull those pieces together is Discover Life in America, a nonprofit established to manage the inventory.

As we walk through a thick, second-growth forest of yellow poplars, hemlocks, hickories, and dogwood, past a scattered crop of pulpy mushrooms that eastern box turtles have nibbled, and toward one of the gurgling creeks that helps drain the Smokies of their moisture, Todd Witcher, Discover Life’s executive director, explains the value of chronicling the life within this biological ark. Only through assembling this ecological jigsaw puzzle, Witcher says, can we really gain an understanding of how the park’s ecosystems function. “Obviously, if we find out what’s here, you have to go back and look at how is it changing?” he says. “Is it disappearing? Is there something else affecting it? Is there another hemlock woolly adelgid out there that’s attacking something else that’s a valuable part of an ecosystem that will change the whole ecosystem? If the hemlocks all disappear, then the whole ecosystem is different than it was 10 years ago, so what happens? What disappears? What rises up and fills in that void?”

That question remains to be answered. One that’s easier to explain is why so many species new to science and the park have been discovered in a landscape that white settlers moved into in the 18th century and that was heavily logged deep into the 20th century. The species are both longtime residents that have symbiotic roles as well as relative newcomers that have disrupted the ecosystem. Chestnut blight, which arrived in the early 1900s from Asia, has virtually wiped these all-American trees from the park’s landscape, and the hemlock forests are vanishing because of the woolly adelgid, another Asian immigrant. Yet outwardly, Witcher notes, some might not consider Great Smoky that sexy of a research lab. “Even though this park is right at our back door and it’s convenient to everybody, scientists haven’t studied here that much,” he explains. “There’s a real appeal for the tropics, for island research, and South America.”

Researchers drawn to the park soon discover that it overflows with habitats, making it a biological crucible. Five different forest types cover the mountain flanks; both grassy balds and heath balds poke holes in the woods near the summits; and vegetative tangles produced by the vigorous growth of catawba and rosebay rhododendrons, magnolia, ferns, holly, and mountain laurel abound. There are even caves that worm into the karst formations underlying the Smokies’ extreme western portions. Spend time roaming from the park’s 870-feet-above-sea-level basement to its 6,643-foot-high Clingmans Dome and you will, in essence, have negotiated diverse vegetative topography akin to what you would find hiking the Appalachian Trail 2,175 miles, from Georgia to Maine.

How the Smokies’ rich assemblage of flora and fauna got there and why in many instances it’s thriving involve ancient climate change and topography. Before the great melt of the last ice age began about 10,000 years ago, glaciers pushed far to the south across North America. While stopping just short of plunging the southern Appalachians into a deep freeze, they herded countless avian, mammalian, reptilian, amphibian, insect, and even plant species ahead of them toward warmer, more hospitable habitats. When the ice flows retreated, those species stayed behind, finding refuge in the Smokies. Some that now thrive in the cooler climate near the park’s roof, such as velvet-leafed blueberry and the spruce-fir forest, are more typically found hundreds of miles north.

Setting out from the lush valley of Cades Cove, it’s an arduous up-mountain, five-mile hike along a trail worn by generations of feet to Spence Field, a clearing atop the park’s spine just below 5,441-foot-tall Rocky Top. From here my eyes sweep out across an undulating mountain range that trends northeast to southwest. This tilt allowed species to move south ahead of the glaciers and find new habitats that suited their needs. Had the mountains been stretched more fully east to west, they likely would have blocked this ecological escape and a lot of species might have been lost to the ice age. Instead, many of them are alive and well in the Smokies, particularly in the section protected within the national park’s borders.

This bulldozing of life left the landscape with tree species in numbers equal to or exceeding all those of Europe, and nearly 1,600 flowering plant species. Even though scientists have been digging deeper and deeper into the park’s aquatic and terrestrial landscapes, the overall richness and depth of biodiversity remains to be fully understood. The ATBI has so far identified about 9,000 species; scientists speculate the park could have as many as 100,000.

Trying to grasp all the measures of life—native and nonnative—within the park’s borders has been intense. The inventory has revealed the obvious species: the black bears, white-tailed deer, and elk. It has also unearthed life-forms that, while out of sight, help keep the overall ecosystem in balance. Though bugs, bacteria, and fungi tend to be afterthoughts when you consider the elements of a healthy ecosystem, they are among the key drivers here. They pollinate plants; keep the organisms they parasitize in check; feed birds, reptiles, fish, and amphibians; and, in the case of worms and other soil dwellers, cultivate the park’s loamy foundation.

They also can be pests, which makes it valuable from an economic perspective to understand them. That’s what brought Gary Steck to the Smokies in 1999. A taxonomic entomologist for the Florida Department of Agriculture, Steck’s interest lies in, among other things, fruit flies: apple maggot flies, cherry maggot flies, blueberry maggot flies, and hundreds of others.

In eight years Steck and his colleagues have expanded the roster of fruit flies in the Smokies from 10 species to more than 50. “Every time we go we come up with something astounding,” says Steck, who recalls one trip that seemed to be a bust until a last-second stop yielded a fruit fly whose day-to-day existence was unknown. “A lot of these astounding finds we made were things that may have been known from as few as three or four specimens in museums. They had never been collected or described. And some of these, it turns out, are actually abundant in the park. So what you find is that while they were seemingly rare, once you know where to find them, they’re not rare at all.”

Better understanding the flies’ ecology, such as the range of plants they thrive on, can help agriculturalists combat the insects. “It’s a big problem we face in Florida,” explains Steck. “A lot of these fruit flies have extremely broad host plant capabilities, so that they can attack not just citrus, for example, but maybe dozens or even hundreds of other fruits. So knowing about alternate host plants is really important.”

Some species that have turned up in the park have been on earth for so long that it’s surprising so little is known about them. Take, for example, water mites, which have been around for 250 million years. An aquatic relative to terrestrially rooted spiders, most of us have unknowingly encountered water mites as we’ve walked through ponds, lakes, and streams. “If you realized how much stuff was in [the water], you wouldn’t step in again,” jokes Andrea Radwell, whose forays into Great Smokies waters have led to dozens of discoveries. “But we’re not prey. They don’t bother us. They’re microscopically small and they prey on insects—and thank goodness. You look at the number of insects that emerge from rivers, and it would just be an uninhabitable planet if they all hatched out. Mites are controlling their populations.”

A rich aquatic stretch, when it comes to water mites, is Twin Creek, a gurgling, mossy, boulder-chocked, and densely shaded stream a short walk from the park’s science center. With more than 2,100 miles of streams overall, Great Smoky is amply populated with water mites. Sixty genera have been documented so far, and almost every major genus that occurs worldwide has turned up here.

With his tall, barrel-chested frame, thick beard, and handlebar mustache, Keith Langdon looks the prototypical national park ranger. Sitting in his office in the Twin Creeks Natural Resources Center, the Great Smoky biologist and ATBI point person sifts through slides of some of the park’s unique, and often unseen, fauna. The Twin Creeks area, which draws its name from LeConte Creek and Scratch Britches Branch, is one of the most biologically diverse sites within the park, he explains. “It’s sort of a surprise, because it’s second-growth forest. Portions of it used to be cornfields.”

You can thank the park’s 100 native tree species, many of which have reclaimed the former cropland since the park was established in 1934, for contributing substantially to the richness. High overhead the forest’s canopy—knit together by eastern hemlocks, beech, red oak, basswood, hickory, and other softwood and hardwood species—blots the sun and holds within the forest moisture that evaporates from the cascading creeks or transpires from the thick vegetative blanket. And there’s a lot of moisture to be captured. On average, seven feet of rain and snow falls here each year. Along with stoking the park’s waterways, this moisture nourishes everything from more than 200 bird species to hellbenders, a curious, oversized member of the salamander family, to slime molds, often-microscopic growths that “bloom” after rainy weather.

Fungus-like although not true fungi, slime molds can be found in moist vegetated settings, where they eat bacteria that engineer decay, helping nutrients cycle through the ecosystem. Usually hard to see with the unaided eye because they’re Lilliputian, under a microscope these molds appear like miniature forests in hues of green, black, coral, red, yellow, or gold. They disperse through their wind-borne spores. During the “fruiting” process that produces the spores, when slime molds “sprout” to visible sizes, they can be positively breathtaking. You often have to search for these life-forms in the forest duff—flip a rotting log, check the cracks in a well-aged tree stump, rummage through a pile of last fall’s leaves—though sometimes they erupt on a pine bough in such large numbers that they appear as a blob.

“Some of them produce what I would say are some of the most beautiful, intricate, miniature works of art that you can find in nature,” says Steve Stephenson, an ecologist at the University of Arkansas who has devoted himself to studying slime molds in the park since 1982. “They’re truly microscopic organisms, but when they form a fruiting structure you can actually see it without the aid of a microscope. They could be a couple of millimeters tall,” he says, “but the rest of the life cycle, you could walk through a patch of forest and never know they’re there.”

So productive are the Smokies’ forests for slime molds that of the estimated 850 to 900 species known worldwide, about a quarter reside within the park. But so what? What’s the point of a microorganism some refer to as “dog vomit”? “Anywhere there are plants, you’re going to find slime molds,” Stephenson explains. “A healthy soil has lots of microorganisms in it. You take them away and the soil is not nearly as healthy.” That, in turn, can have a ripple effect on the balance of the larger ecosystem. Scientists are also looking into how slime molds might benefit human health. In laboratory settings the organisms have been used in National Institutes of Health–funded Alzheimer’s disease research, cancer studies, and developmental research, says Stephenson.

The researchers’ findings beg the question: Does the biodiversity spring from the sizable and sprawling ecosystem that cups the park, or is it there because the park has protected these habitats from the pressures of development?

“There’s certainly a great diversity of habitat there. You’ve got the elevational gradients, and then the heavy forests, the big open meadows. So the diversity is part of it. Management of the park is part of it,” answers Steck. “One thing that is a little bit curious is that some of these flies were thought to be very rare, and we find them abundantly in the park. [But] outside the park we’ve had trouble finding them.”

It could be, he says, that the effort to tally species outside the park doesn’t nearly match the effort inside. Or perhaps it’s the bias of their collecting. Or it could be that development and agricultural chemicals outside Great Smoky leave the park as a sort of refuge.

If Great Smoky Mountains National Park is indeed an ecological ark, then the Twin Creeks Natural Resources Center might be considered its hold. When I return there park ranger Langdon guides me through curatorial rooms where tens of thousands of species of moths, butterflies, beetles, bees, plants, snakes, salamanders, fish—even a mounted passenger pigeon—are stored. Finally, we enter a workroom where a map of the park is tacked to one wall. Glancing at the map, Langdon says he looks forward to the day when, thanks to the ATBI, he’ll essentially be able to throw a dart at it and tell you what life can be found where it lands. But he also hopes that America realizes before it’s too late that riches await them across the nation. “This diversity is found in a lot of different places,” he tells me. “We can’t predict where it’s found. The country needs to get to work.”